Processes and apparatus for dewatering aggregates typically use worm presses, screen belt presses or the like. The apparatus is initially filled with pre-dewatered solid suspensions or slurry, and in particular, fiber suspensions, by means of conveying systems, such as, for example, conveyor belts. In these devices, controlling the speed and discharge rate of the dewatering apparatus is by either maintaining a constant level in the inlet chute or by maintaining a constant back pressure in the outlet of the dewatering apparatus. The known control systems for monitoring, processing and controlling the extent of dewatering of the suspension suffer from the major disadvantage that when the solid suspension supply varies during the process, the suspension is not effectively dewatered. For example, when the supply rate is too high, the suspension is not dewatered quickly enough so that the material supply system becomes choked and overflows. When the suspension supply rate is too low, the dewatering apparatus runs dry because of insufficient supply of suspension. These processing deficiencies reduce the efficiency of the system and produce a non-uniform output.